Method and preparations for the permanent dyeing of keratinous material



United States Patent 2,776,663 METHQD AND PREPARATIGNSFOR THE PERMA NENTDYEING 0F KERATINOUSMATERIAL William E. Morgan, Ridgefield, N. 1.,assignor to Helena Rubinstein, Inc., New-York, N.- Y., a corporation ofNew York No Drawing. Ap lication'June'ZS, 195i, Serial No. 234,156

1 18 Claims. (Cl. 132-7) for human skin and with neutral or moderatelyalkaline" solutions which are=harmless to the-hair as wellas to theskin.

A further object of the invention is to provide a method for permanentlydyeing keratinous material, and' particula'rly humanhain-under suitableconditions withnon i toxic coal-tar dyes, in--such a manner that thecolor is' securely fixed in the dyed materialandcannot b removed byrubbing, washing or shampooingi- A still further object ofthe-inventionis to providea method 1 for permanently dyeing human hairwith nontoxic dyes in-a manner to permit permanenbwaving'bf' the dyedhair without change of the "color imparted -to the hair and without hairdamage.

A still further object of theinvention is to providefa methodforpermanently dyeing human hair with entirely non-toxic and harmlessdyes, which methodis ea'sy'and" safe 'in its application, satisfactoryin its results; and does not require either a pre-treatrnent oran-after-treatment" ofthe hair; i p

Still'a further object of the invention is to provide'a method ofpermanently dyeing human hair by means of the dyes which areknown ascertified colors and Which heretofore have not been successfully usedfor this'pui pose; l

Still anotherobject of the invention is to produce a preparation for thepermanent dyeing of keratino'usmaterialg andparticularly' of human hair;which can be applied to-the"*hair in a simple manner and which producesth'e desired coloringeasily andsafely andwithout undesirable orharmful side eflec'ts or after'effectsi A special object of theinvention is to produce a preparation-forthe-permanent dyeing ofkeratinousmaterial, andparticularly of-human hair, which consists oftwo" separate solutions to be mixed immediatelybefore appli-' cation tothematerial to be' dyed, and which yields a mixture producing thedesired coloring effect by'means" of-cer'tifiedcolors'in a reliable,safe'and permanent man-' Another specialobject of the invention is toproduce" a preparationfor"the permanent dyeing of 'ker'atinous" materiaLparticularly of human hair, which consists-of a dry, powdery mixture ofseveral water-solublein gredients which, on dissolution in apredetermined amount 2,776,668 Patented Jan. E, 12957 of water, yield'adye solution applicable directly to the material to be dyed to producethe desired coloring by means of certified colors in a simple and safemanner.

These" and other objects, which will appear in more detail as thedescription proceeds, are accomplished according to my invention by themethods and preparations described hereafter and defined in the appendedclaims.

Throughout the following description the term by weight of the solution"is used to indicate that a specified number' of parts by Weight ofsolute is present in parts by'weight of solution. 7

Generally, the dyeing method according to my invention comprises thesteps of treating the material to be dyed "with a freshly preparedneutral to mildly alkaline, aqueous solution containing a smallpercentage of a water-soluble mercapto compound and, as sole coloringagent, a dyestufi of the group consisting of the Ext. D & C, D & C and FD & C certified colors and mixtures thereof, washing the dyed materialwith an aqueous medium, and drying'it.

Heretofore, certified colors could be used for the perm'anent' dyeing ofkeratinous matter only in strongly acid or" strong salt solutions, andat elevated temperatures. As 'a result, difficulties arose in the use ofsuch dyes for some purposes and, particularly, they could not beemployed' for the permanent dyeing ofthe hair of living persons unlessthe hair was subjected to complicated pretreatments or after-treatments.

The'pr esent'inventionis based on my discovery that the Ext. D & C, D &C and F D & C certified, non-toxic coal tar dyes are suitable for thepermanent dyeing of keratinous material at moderate temperatures and inneutral or mildly alkaline solutions, if a relatively small percentageof water-soluble mercapto compounds is added to the dye solutionsimmediately before they are used. Myinvention makes it possible to dyehuman hair in a simple manner permanently with dye preparationscontaining" exclusively completely harmless and safe ingredientsand toproduce natural, predictable color shades which arefast to rubbing,washing, shampooing and permanent waving.

While I do not wish to be bound by any specific theory, my experimentsseem to indicate that the mercapto compoundsfacilitate the transport ofthe dyestuffs directly into the cell structure of the keratinousmaterial to be dyed and thusinsure a thorough penetration and fixationof the dyes in the material to be colored.

I havefound that hair substance itself, under the action of dissolvedmercapto compounds in neutral or weakly alkaline aqueous solutions,absorbs not only water, but other substances dissolved in the aqueousmixture, such as dissolved dyestufis. The size of the dyestufi moleculesand'the diffusion velocities of the dissolved substances seem to havelittle or no influence on their transportation. Even'in the presence ofrelatively small proportions of mercapto compounds, the dyestuffs do notform merely a filter cake 'on the exterior of the hair shaft, which isremovable by rubbing or washing, but pass with the liquid into theinterior of the hair. The substances migrating with the water ortransported thereby become effectively trapped or imbedded in the hairsubstance and are not subject to removal by customary treatments, suchas rubbing, toweling, washing, shampooing or permanent Waving;Microscopic examination has shown the hair fibers to be uniformlystained over the areas between the imbrications.

The expressions Ext. D & C, D & C and F D & C certified colors or simplycertified colors as used in myspecification and claims is intended todesignate the coal tar dyes which are certified as permissible and pureby the Federal Food and Drug Administration. Such colors are certifiedas F D & C where they are per- 3 missible in Foods, Drugs and Cosmetics,as D & C where they are permissible in Drugs and Cosmetics, and as Ext.D & C where they are permissible in Drugs and Cosmetics for externalapplication only.

It has been found that dye solutions suitable for the dyeing ofkeratinous material according to my invention may contain preferablybetween about 0.033 and 6.2% by weight of the solution of suchdyestuffs.

The water-soluble mercapto compounds to be used in the dye solutionsaccording to my invention are particularly the water-soluble mercaptocompounds of the general type useful for hair waving and depilatorypurposes. Suitable examples are thioglycolic and thiosalicylic acids inthe form of their water-soluble salts, thioglycol, thioglycerol andthiophenol. At present, I prefer in most cases to use thioglycolic acidbecause it is readily available, has no intense objectionable odor, andis ordinarily entirely harmless in the concentrations in which it isused according to my invention, but I do not limit my invention eitherto this or to any other particular mercapto compound. The water-solublemercapto compounds are present in my dye solutions in quantitiesequivalent with respect to S H group to about 0.1 to 6% by Weight of thesolutions of thioglycatic acid. For hair dyeing purposes, a mercaptocompound content equivalent with respect to S H group to between about1.2% and about 6% by weight of the solution of thioglycolic acid hasbeen found to give most favorable results.

The temperatures used in my dyeing processes may vary between about 50and about 110 F. Temperatures of between about 60 and about 80 F. arepreferred, particularly in the use of my invention for the permanentdyeing of human hair.

The dye solutions according to my invention are applied to thekeratinous material at a pH value between about 6.6 and about 11.3 andpreferably at a pH value of between about 9 and 10.2. As basis for theestablishment and maintenance of the desired pH values, I havesuccessfully used concentrated aqueous ammonia, sodium hydroxide, sodiumcarbonate in the presence of ammonium chloride, ethylene diamine, andtriethanolamine. Other alkalies could undoubtedly be employed. For mostpurposes, I prefer to use concentrated aqueous ammonia and sodiumhydroxide either separately or in suitable mixtures.

In general, I have found predominantly aqueous solutions of dyestuffsand mercapto compounds well adapted for color transportation into andcolor fixation in hair. Small additions of water miscible organicsolvents, such as propylene glycol, ethyl alcohol, tetra-hydrofurfurylalcohol or the like may be advantageous in order to improve thesolubility of the coal tar dyes.

Useful effects in coloring hair are accomplished at temperatures ofbetween about 60 F. and about 80 F. with relatively weak solutions ofmercapto compounds and usually at mild alkalinities. I have foundadequate, for example, up to about 4% by weight of the solution ofthioglycolic acid at alkalinities corresponding to pH values of not morethan about 10.5 during 15 to 25 minutes. Many of my successful hairdyeings, accomplished without evidence of any resultant hair damage havebeen performed with less than 2.6% by weight of the solution ofthioglycolic acid in the form of its sodium salt, with excess of ammoniaas free base at pH values of about 9 to 10 at a temperature of about 68F. within about to minutes. This combination of conditions lies wellwithin allowable extremes and may be adopted as normal. Increase abovenormal in any of the three principal factors, namely, concentration ofmercapto compound, alkalinity in pH terms, and temperature, intensifiesnot only the resultant coloration, but also the action of the remainingunaltered factors upon the hair substance. With increase toward higherextremes of these factors, and particularly when large increases in twofactors occur together, hair substance may tend to absorb excessiveamounts of water with undesirable swelling, distortion and softening ofthe hair. The fiber may thereby be weakened and actual disintegration ofthe hair may occur unexpectedly on washing or combing. An unfavorableresult caused by the elevation of one factor above normal may often beforestalled by expedient lowering below normal of one or more of theother factors. If considerably high concentrations of mercapto compoundsare employed, such as, for instance amounts equivalent with respect to SH group to 4.5 to 6% by weight of the solution of thioglycolic acid,then alkalinity should be adjusted to a lower pH value, for instance,9.4 or less to preclude irreversible hair damage. If a high temperatureis employed, such as, for example, 110 F., then a moderate concentrationof mercapto compound, for instance, in the range of up to about 2.5% byweight of the solution of thioglycolic acid, may require lowering of thepH value below 9.3 in order to preclude hair damage. For example, verygood hair coloration, without any evidence of hair damage, may beeffected with 2.5% by weight of the solution of thioglycolic acid actingupon hair at 110 F. during 15 minutes at a pH of 8.0. Decrease belownormal of any of the three factors diminishes the risk of hair damagebut weakens correspondingly the resultant coloration. Thus with colorsolutions, for instance, in the neighborhood of 50 F., coloring actionis appreciably less than at 60 to F. for 1.4% by weight of the solutionof thioglycolic acid at a pH of 9.4 acting during 20 minutes. With 0.5%by weight of the solution of thioglycolic acid, coloring action isappreciably less than with 1.4% by weight of the solution ofthioglycolic acid, other conditions remaining the same for both cases.At a pH value of 7.7, coloring action is appreciably less than at a pHof 8.5 for 2.5% by weight of the solution of thioglycolic acid at 70 F.during 20 minutes. Minima for concentration of mercapto compound, pH,and temperature are not imposed like maxima, by the susceptibility ofhair to damage, but are chosen when low values for one or more factorsrequire considerable increase above normal in one or more of theremaining factors for good and intense coloring of the hair.

Contact between hair and dye solution should be maintained for at leastseveral minutes. A period as short as above five minutes may produceappreciable coloration of the hair, but with tinting action during sixminutes, the resulting coloring is appreciably weaker than with tintingaction during fifteen minutes for 2.5% by weight of the solution ofthioglycolic acid at 70 F. and a pH value of 9.4. Ordinarily, it is notnecessary or desirable to maintain the hair in contact with the dyesolution for more than a maximum time of thirty-five minutes. However,where the pH value of the solution is low or the temperature used isbelow 70 F., contact times of from 1 to 2 hours may have no detrimentaleffect on the hair, although generally, after the first thirty minutes,no significant increase in intensity of coloration has been observed.

I have found that in the dyeing of human hair, it is preferable to usesolutions containing, in addition to the dissolved dyestuffs, an amountof mercapto compound equivalent with respect to S H group to about 1.2%to 6% by weight of the solution of thioglycolic acid.

Preferably the solutions have a pH value between 6.6 and 10.4 but nothigher than 9.4 when the mercapto concentration is equivalent to atleast 3% by weight of the solution of thioglycolic acid and not higherthan 9.15 when the mercapto concentration is equivalent to at least 5.6%by weight of the solution of thioglycolic acid. The solution is appliedto the hair at a temperature of between about 50 F. and F. but not lessthan 70 F. when both mercapto concentration and pH value approach theirminimum values and not higher than 80 F. when both mercaptoconcentration and pH value approach their maximum values.

According to a preferred embodiment of my invenarm-see.

tion, the mercapto content of, thensolution .is. kept below aboutj4%.,byweightsof the solution. This .hasthQadVan-x tage that thehairiswnotappreciablyafiiected bythereduce.

ing action of themercapto, compounds and, consequently, no oxidizingafter-treatment of thedyed materialris necessary. After the dy'feingoperation.itself,..the ,dyed. ma: terial is sirhplylrinsed with-water toremove the..excess dye in order to. producea permanent coloringwhich is.fastagainst rubbing; or shampooing. However, .it .is possible,

to, use solutionsncontaining morezthan about 4%. and .up to..about,6% byweight of the solution of water-soluble mercaptocompounds. In thesecases the dyed material,

afterapplication of thedye solution thereto,.is preferably treatedwitha, mild oxidizing. agent,: such ashydrogen peroxide.

While. most of thecertifiedcolors when used in accordance withmyinvention. willproduce ,the desired-color values on. hair-with haircoloring. effects which. are "fast to. rubbing,.,washing, shampooing andpermanent waving without any after-treatment, in some .cases it may.be-usee.

ful to apply to the dyed hair an after-treatment for the purpose ofcolor development, color intensification or improved color fixation.Mild oxidizing agents; suchas hydrogen peroxide, and acids, such asacetic acid, may be used in these cases, which :are within thebroadscope of my inventiomfor after-treatment of the dyed hair.

My invention also covers the new preparations for the permanent dyeingof keratinous material to be .used in...

my method. Such preparation maybe, for instance, a'

neutral or mildly alkaline solution containingsin am aqueous solvent asmall percentage of a water-soluble: mercapto compound and, as solecoloring agent, a dye-r stufi of the group consisting of the Ext. DI&,C,D1 8: C. andF D"&' C certifiedcolors and mixtures thereof Preparationswhich are intended for the dyeing of human hair contain preferably aquantity of: wateresoluble mercapto compound equivalent withrespect toSH' group toabout 1.2%"to6%-' by weight-of the solution-of' thioglycolicacid and have a pH value of "between*6.6 to 10.4 but not higher than 9.4when the mercaptoconcentration is equivalentioat least 3%- by weight ofthe. solution of thioglycolic acid and not higher than:.9.15. when themercapto. concentrationis equivalent to at least 5.6%..by weight of thesolution of thioglycolicacid.

Sincemany of the certified colors may deteriorate if they remain in asolution containing-mercapto compounds for any. length of time, it isessential that-the dye com ponents of the solutions are combined withthe-mercapto components immediately before application. to thekeratinous material to be dyed. Preferably, the dye mercapto solutionsare freshly prepared from two sepae' rate starting solutions immediatelybefore they are used. Thus, a preparation of :the dyeing of keratinous.material,. and particularlyrof human hair, may comprisea' of. the twosolutions,; the total-quantity of solvent in both solutions and therelative proportionsof the solutions being such that the resultingmixture is neutral or mildly alkaline and contains a small percentageofa watersoluble mercapto compound.

According to another embodiment of my invention, .a preparation for thedyeing of keratinous materiaLand particularly of human hair, may be asubstantially dry powder mixture comprising a dry, water-soluble solidmercapto compound, an ammonium salt, a dry, weakly alkaline,water-soluble salt of an alkali-metal, and,:'as:

sole coloring agent, a dry, wateresolubledyestuff selected from thegroup consisting of. the Ext. D & .C,.D;& Cand.

F D & C certified .colors andmixturesrthereof, the-several ing edients.being, present. in .such. proportions that, an. addition thereof 'to apredetermined.quantitywof water;

a dye solution is formed which contains a small percentage of mercaptocompound and is neutral or mildly alkaline.

The following examples are intendedto illustrate the invention withoutlimiting its scope, and to show clearly, the absence of transportofdissolveddyesuifs" into the hair and other keratinous material "in theabsence of mercapto compounds in contrast to the immediateactiva tion ofsuch .transportof dyestuifs'in the presence of small percentages ofmercapto compounds under otherwise identical conditions.

Example -I Firm textured, nearly colorless human hair was immersed for15 minutes-at a temperature of F., with exclusion of air, in a solutioncarrying,0.920g.. of a dyestufi'mixture consisting of:

D &.C.Black. #1 (0.1. 246) D. &.C.Brown #1 (C. L234) Ext.-.D:&C:Reds.#.13 (01.252)

4.0 mLconcentrated ammonia water q. s. water to make 102 ml.

After 15 minutes the. hair was next immersed for .15 minutes in 20volume 'hydrogen'peroxide in 7 percent acetic acid, thenfinallytshampooed and'toweled. The hair retained a pale'grjaycoloration; No appreciabledyeing of the hair hadbeen accomplished.

10 ml. of ammoniacal thioglycolate solution were then." added to thepreviously described solution, the resulting, mixture havingsubstantially the following composition? 0.920 g. dyestutf mixture 1.4g.-thioglycolic acid 6.0 ml. concentrated ammonia water q. s. water tomake 112ml. pH-9.5

The thioglycolic acid content of the mixture'amount ed by weight of thesolution and the" dyestuif content amounted to-0.8% by weight of thesolution.

For comparison,- hair 'of the same character was simi larly immersed for15 minutes at 70 F. with exclusion' of airain this solution After 15minutes, the hair was next. immersed for 15 minutes in 20 volumehydrogen: peroxide in 7 percent acetic acid, then finally shampooed and.toweled. The hair retained a moderate ash blonde coloration,approachingtbrown, but lacking warmth or redness. A permanent dyeing hadresulted.

Example [I Firm textured, nearly colorless human hair was satu- Yrated=for 3 minutes in a solution containing 3.89 g. of a dyestuffmixture consisting of:

D & C Black #1 (CT. 246) F D & C Yellow #5 (C. I. 640)* Ext. D & C Red#8 (Cl. 176) D & C Red #33 (C. I. 30)

4.0 ml. concentrated ammonia water q. s. Water to make 86 ml.

The hair was then exposed for 15 minutes to the atmosphere While wet.Cooling of the solution during the exposure period took place, theaverage temperature being estimated to be about 60 F.

After 15 minutes the hair was in part merely rinsed and blotted, thendried, in part well-shampooed, then rinsed, blotted and dried. Therinsed hair retained a pale pink-violet coloration,- the shampooed haira distinctly paler pink-violet coloration; Most of the pale coloradhering' to the merely rinsed hair was located superficially and-wasremovable by shampooing. The hair .was not permanently dyed.

Upon addition of 10 ml. of ammoniacal thioglycolate 7 solution to thisdye solution, a mixture resulted which had the following composition:

3.89-g. of dyestuff mixture 2.5 g. thioglycolic acid 1.1 g. sodiumhydroxide 7.41 ml. concentrated ammonia aqua q. s. water to make 96 ml.pH9.25

In this mixture, the thioglycolic acid content amounted to 2.6% byweight of the solution, the dyestutf content to about 4% by weight ofthe solution.

For comparison, hair of the same character was similarly saturated for 3minutes and then exposed wet for 15 minutes to the atmosphere underidentical temperature conditions estimated on the average to be about 60F. After 15 minutes, the hair was in part merely rinsed and blotted,then dried, in part well shampooed, then rinsed, blotted and dried. Themerely rinsed hair retained a strong violet-brown coloration, theshampooed hair likewise a strong violet-brown coloration, hardlydistinguishable from that of the merely rinsed hair. The hair wassubstantially dyed.

Example III A solution was prepared containing:

0.320 g. D & C Black #1 (C. I. 246) 0.800 g. D & C Orange #3 (C. I. 27)0.700 g. Ext. D & C Red #13 (C. I. 252) Total 1.820 g. dyestuff mixture25.0 ml. propylene glycol q. s. water to make 90 ml.

To this solution was added immediately before use ml. of ammoniacalsodium thioglycolate solution containing:

2.5 g. thioglycolic acid 1.1 g. sodium hydroxide 3.4 ml. concentratedammonia aqua The resulting 100 ml. solution had a pH of 10.1. Thethioglycolic acid content was 2.5% by weight of the solution.

This mixture was immediately applied at a temperature of 68 F. touucolored human hair, conveniently by a brush. the wet hair was allowedto remain exposed to the atmosphere for 20 minutes at a temperature atwhich the wet solution was maintained substantially constant at 60 F.Thereafter, the dark excess of dye was rinsed from the hair with Warmwater until the washings were substantially colorless. The hair was thengently toweled and finally dried with a warm air current. The hairretained a natural and pleasing dark auburn coloration. It wassubsequently gently shampooed with only an insignificant change of haircoloration resulting from even the first shampooing.

Example IV 0.800 g. D & C Black #1 (C. 1. 246) 0.600 g. D & C Orange #3(C. I. 27)

0.500 g. F D & C Yellow #6 (a dyestutf obtained by coupling diazotizedsulfanilic acid with 2-naphthol-6-sulfonic acid) 1.000 g. Ext. D & C Red13 (C. I. 252) Total 3.900 g. dyestuff mixture 25.0 ml. propylene glycol1.1 g. sodium hydroxide 1.7 ml. of concentrated ammonia aqua weredissolved with water in a volume of 90 mls., pI-I12.15

To this solution was added, immediately before use, 10 ml. ofsubstantially neutral ammonium thioglycolate solution, carrying 2.5 g.thioglycolic acid to make 100 ml. solution having a pH of 9.7.

The mixture was immediately applied at a temperature of about 77 touucolored hair conveniently by a brush. Thejwet hair was allowed toremain exposed to the atmosphere for 20 minutes at a temperature atwhich the evaporation of the water caused some cooling down of thesolution. The average temperature of 20. minutes exposure time wasestimated to be about 75 F.

After 20 minutes, the dark excess of dye was rinsed from the hair withwarm water until the washings were substantially colorless. The hairthereafter was gently toweled and finally dried with a warm air current.The hair maintained a permanent, dark brown, very natural coloration.

In some cases, where very intense hair coloration is desired, not all ofthe dyestuffs participating in the. final color-quality remain reliablycompatible in high concentrations. In such cases a repeated treatment ofthe hair with a weaker dye mixture may be convenient, employing in eachtreatment a dye mixture, with a smaller proportion of mercapto compound.This may be illustrated by the following:

Example V A mixture was prepared of:

2.4 g. D & C Black #1 (C. I. 246) 1.7 g. D & C Orange #3 (C. I. 27) 2.1g. Ext. D & C Red #13 (C. I. 252) Total 6.2 g. dyestufi mixture 25.0 ml.propylene glycol q. s. water to make 93 ml.

To this mixture is added, immediately before use, 7.0

ml. of ammoniated sodium thioglycolate solution, carry- The mixture wasat once applied to uucolored hair, conveniently by brief immersionthereof, and the wet hair allowed to remain exposed to the atmosphere ata temperature of 66 F. for 20 minutes. Thereafter, the dark excess ofcolor was rinsed from the hair with warm water, until the washings weresubstantially colorless. The hair was then gently toweled and dried in awarm air current. The hair retained a dark brown coloration, nearly ablack. Immediately thereafter, a portion of the dyed and dried hair wasidentically treated with an identical mixture of the same quantities ofthe same dyes as above, freshly mixed with 7 ml. of the same sodiumthioglycolate solution. After 20 minutes exposure of the wet hair to theatmosphere at 66 F., the hair was simi-, larly rinsed as above, toweledand dried. The hair retained a black coloration. No hair damage wasevident.

Example V1 2.4 g D & c Black #1 c. I. 246) 1.7 g. D & 0 Orange #3 c. I.27 21 g. Ext. D & c Red #13 c. I. 252

Total 6.2 g. dyestutl mixture was dissolved in a solvent containing:

25.0 ml. propylene glycol 1.5 g. sodium hydroxide 4.0 g. thioglycolicacid 2.86 ml. concentrated ammonia aqua q. s. water to make ml. pH-9.45

In the fresh mixture, firm textured, nearly colorless human hair wassaturated for 3 minutes at a temperature of about 74 F. and then exposedto the room atmosphere for 20 minutes in Wet condition. Over the entirecontact period of 23 minutes, the solution had on the average a tmperature of about 66F. At theend of the- 20 m utep iold. he i Was s ifiedwwi h Warm wa er n r d-Y he. h r. e imi a e ut fu a k. w browncoloration,,and;there was. no indication of damage to; the hair.

' Example VII 3 yes utlv ixtur aving the. amecomposition as in thepreceding example were dissolved in a solvent containing:

25.0 ml. propylene glycol 2.0 g. sodium hydroxide 5.5 g. thioglycolicacid 3.86 ml. concentratedammonia aquav q. s.. water. to make 100 ml.

In the fresh' mixture .firmtextured,.nearly colorless human hairwassaturated forfi minutes at about. "74 F., then exposed to roomtemperature for 20 minutes in wet condition. The over all temperature ofthesolution throughout the contact time of 23 minutes was about 66 F. Atthe expiration of the 20.."minuteperiod, the hair was, -rinsed,, thentreated for. 10 .minutes at a. temperature of about 68 F. with 5 volumeshydrogen peroxide solution carrying 3% of-aceticacid. After lfinalrinsing and drying, the hair retainedea very. darkbrown coloration,

almost a black. No indication of hair damage appeared at .any stageoftreatment.

Example VIII 6.2 g. of -a dye mixture 1 having the; same. composition asin the preceding, two exampleswere dissolvedin a solvent; containing:

25.0 ml. propylene glycol 2.2 g. sodium hydroxide.

6.0 g. thioglycolic acid 4.21 ml. concentrated ammonia. aqua q.. s.water to .malge 100 mlpH-9.15

In the fresh mixture, firm textured, nearly colorless human hair wassaturated for 3 minutesat79 F. and then exposed. to the roomatmosphere-for 20-minutes in' wet condition. The average temperatureover theentire 23 minutes of contactwas about 66 F;

At the end of 20 -minutes--exposure, the hair was rinsed, then treatedfor minutes at room temperature with 5 volumes of hydrogen-peroxide=solution carrying 3% of acetic acid; finally rinsed and dried. The-hairretained a very dark, drabbrown coloration, almost a black. There wasnoindication of hairdamage apparent atany stage ofthe treatment.-

Example .IX.

A- solution was preparedqcarryingz 0.50 g. D & C Violet #1 (C. I. 697)2.5 0 g. thioglycolic acid 1.1 g. sodium hydroxide 7.41 ml."concentrated ammonia aqua q. s. water to make 100 mLpH' 10.4

In the fresh solution firm textured, uncolored human hair wassaturatedfor 3 minutes at. abouty73 F., then exposed in. wet ,conditionto. the. room-=;atmospl1ere1 for minutes. During the entire contact timeof 23 minutes,

the average temperature of the solution was about 64 F. Thereafter, thehairwas well rinsed'and dried. It re-. tained apermanent pronouncedbluecoloration;

Example X A solution was prepared'carrying:

0.50 g. D & C Violet #1 (C. I. 697) 2.50 g. thioglycolic acid 2.55 ml.concentrated ammonia aqua q. s.. water to make100. ml. pH-.8. 52,

In the fresh mixture, firm textured, colorless human. hair was saturatedfor 3 minutes at a temperature of about.

76 F. and then exposed in wet condition to the. room atmosphere for 20minutes. The average, temperature of.

the solution throughout the total exposure time of 23 minutes wasestimated to be about 68 F At the end of "the 201minutes, the hairwaswellrinsed and dried. The hair: retained a pronounced blue .coloration, slightly, duller-and a little more reddish than the.

final blue ofExample- IX.

Example XI A solution was prepared carrying:

0.250 g. D & C Black #1 (C. I. 246) 0.600 g. D &C Orange-#3'(C. I. 27)

0.500 g. F D & C Yellow #64 a dyestutf obtained by coupling diazotizedsulfanilic acid with 2-naphth0l-6-sulfonic acid) 0.300g. Ext. D"& C Red#13 (C. 1.252) Total 1.650 g. dyestufi mixture- 25.0:m1. propyleneglycol 2.5 gl; thioglycolic acid 1.1 g. sodium hydroxide 3.41 ml.concentrated ammonia aqua q. s. water to make ml. pH9.40

The fresh solution was chilled to 50 F. and firm.

textured, uncolored human hair was immediately immersed therein at 50 F.for 15 minutes. Thereafter the hair was rinsed, blotted, and 'dried. Thehair retainedapale, golden blonde coloration, very natural.

Example XII A solut-ion was prepared, carrying 1.65 g. of adyestufif:mixture; having the same composition as in- Ex: ample XI; and

2510 ml. propylene glycol 2.5 g. thioglycolic acid,

2.95 ml. concentrated ammonia water q. s. water to make 100 iml.pH- 8'.0

The fresh solutionwas-warmedto F., and.; firm textured, uncolored humanhairwas immediately immersed therein at 110 F. for. 15 minutes.Thereafter the hair was rinsed, blotted and dried. The hair retained adark, Warm brown color, very natural. No evidence appeared of hairdamage.

Example XIII 1 A solution was prepared carrying 1.56 g. ofadyestulfmixture having the same-composition as in Example XII, and d 25.0 ml.propylene glycol 2.5 g. thioglycolic acid.

1.95 ml. concentrated ammonia-aqua. q. s. waterto make 100 ml..pH-6.60

Example XIV A solutionv was prepared containing:

0.160 g. D & C Black #1 (C. I. 246) 0.750 g. D & c Orange-#3 c. 1. 270.600 g. F D & C Yellow #6 (a dyestulf obtained by coupling diazotizedsulfanilic acid With- 2-naphthol-6-sulfonic acid) 0.140 g. Ext;D*&-*C"Red #13 (CI. 252) :-Total 1.650 g. dyestufiimixture 25.0 ml.propylene glycol 2.5 g. thioglycolic acid 1.1 g. sodium hydroxide 3.41ml. concentrated ammonia squa q. s. water to make 100 ml. pH9.40

Firm textured, uncolored human hair was dipped in this solution at 68 F.for three minutes and then exposed to the atmosphere for minutes at 66F. The hair was then rinsed, blotted and dried. A permanent dyeing ofthe hair to a light, ash blonde, was obtained.

Repeating the same procedure with exposure times of 10, 20 and 30minutes respectively, the final coloration became progressively moreintense, until, with 30 minute exposure, a very natural, dark ash-blondewith red overtones was obtained.

Example XV A mixture, in powder form, consisting of:

0.250 g. D & C Black #1 (C. I. 246) 0.600 g. D & C Orange #3 (C. I. 27)

0.500 g. F D & C Yellow #6 (a dyestufi obtained by coupling diazotizedsulfanilic acid with 2-naphthol-6-sulfonic acid) 0.300 g. Ext. D & C Red#13 (C. I. 252) Total 1.650 g. dyestutf mixture 3.9 g. calciumthioglycolate, equivalent to 2.4 g. thioglycolic acid 4.5 g. sodiumcarbonatec. p., anhydrous 3.0 g. ammonium chloride, U. S. P. was shakento solution in water to make 100 ml. having a pH=9.4.

In the fresh mixture, firm textured uncolored human hair was saturatedfor 3 minutes at 70 F., then exposed in wet condition to the roomatmosphere for 20 minutes, the average temperature of the solution forthe entire contact time being estimated as 66 F. At the end of the 20minutes, the hair was well rinsed and dried. It retained a beautiful,very natural dark brown coloration.

Example XVI A solution was prepared carrying:

1.0 g. F D & C Green #2 (C. I. 670) 1.0 g. D & C Red #33 (C. I. 30)

Total 2.0 g. dyestuff mixture 1.23 g. ethylene diamine 2.14 g.2-mercapto-ethanol (equivalent to 2.53 g. of

thioglycolic acid) q. s. water to make 100 mL; pH=9.6

Firm textured, uncolored human hair was saturated briefly in the freshsolution and then exposed in wet condition to the room atmosphere for 15minutes at a temperature to retain the solution at about 66 F.throughout the exposure period. Thereafter, the hair was immersed for 15minutes in 4% acetic acid solution, finally shampooed, rinsed and dried.The hair retained a strong bluish red permanent coloration.

Example XVII A solution was prepared carrying:

0.40 g. D & C Red #33 (C. I. 30)

0.40 g. F D & C Blue #1 (C. I. 671 is the ammonium salt) 1.60 g. D & COrange #3. (C. I. 27)

0.25 g. Ext. D & C Red #13 (C. I. 252) Total 2.65 g. dyesturf mixture25.0 ml. propylene glycol 2.63 g. monothioglycerol (1 mcrcapto-2,3propane diol),

(equivalent to 2.24 g. of thioglycolic acid) 3.14 ml. concentratedammonia aqua q. 5. water to make 100 ml. pH=9.8

Firm textured, uncolored human hair was saturated in the fresh solutionat 70 C. for 3 minutes, then exposed in wet condition to the roomatmosphere for 20 minutes. During the entire contact period of 23minutes the temperature of the solution averaged about 66 F. At the endof the 20 minutes, the hair was shampooed, rinsed and dried. The hairretained a coppery red coloration.

Example XVIII A solution was prepared carrying:

0.250 g. D & C Black #1 (C. I. 246) 0.600 g. D & C Orange #3 (C. I. 27)

0.500 g. F D & C Yellow #6 (a dyestufi obtained by coupling diazotizedsulfanilic acid with 2-naphthol-6-sulfonic acid) 0.300 g. Ext. D & C Red#13 (C. I. 252) Total 1.650 g. dyestuff mixture 25.0 ml. propyleneglycol 3.0 g. thiophenol (equivalent to 2.5 g. of thioglycolic acid)3.44 ml. concentrated ammonia aqua q. s. Water to make 100 ml. pH=9.5

Firm textured, uncolored human hair was saturated in the fresh solutionat about 74 F. for 3 minutes and then exposed in wet condition to theroom atmosphere for 20 minutes. The average temperature during theentire contact time of 23 minutes was about 66 F.

At the end of 20 minutes, the hair was rinsed and dried. It retained areddish blond coloration.

Example XIX A solution was prepared containing 1.65 g. of a dye mixturehaving the same composition as in Example XIX, and:

25.0 ml. propylene glycol 4.18 g. thiosalicylic acid (equivalent to 2.5g. of thioglycolic acid) 5.3 ml. concentrated ammonia aqua q. s. waterto make 100 ml. pH=9.6

Firm textured, uncolored human hair was saturated in the fresh solutionfor 3 minutes at 74 F. and then exposed in wet condition to the roomatmosphere for 20 minutes. The average temperature of the solutionthroughout the exposure period of 23 minutes was about 66 F.

After 20 minutes, the hair was rinsed and dried. It retained a light,coppery brown color which was permanent.

In numerous other instances, both with mixtures of certified colors andwith single certified colors, I have established by similar comparativetests that a negligible to slight fixation in hair of color from neutralor alkaline solutions in the absence of mcrcapto compounds, can betransformed into strong and useful fixation in hair of the same colorsmerely by the added presence in the color solutions ofmcrcapto-compounds. Such further instances include:

Ext. D & C Blue #1 (Methylene Blue) C. I. 922

D & C Violet #1 (Wool Violet SBN) C. I. 697

D & C Orange #5 Dibromofluorescein Ext. D & C Yellow #3 (Fast LightYellow) C. I. 636 F D & C Red #1 (Ponceau 3R) C. I.

F D & C Red #2 (Amaranth) C. I. 184

D & C Red #19 (Rhodamine B) C. I. 759

D & C Red #27 (Tetrachlorotetrabromofluorescein) The following examplesare intended to show that Wool can also be permanently dyed with my dyepreparations at ordinary temperatures;

Example XX A solution was prepared containing:

0.300 g. D & C Black #1 (C. I. 246) 0.088 g. D & C Brown #1 I. 234,)0.113 g. Ext. D & C Red.#13 (C. I. 252) Total0.501 g. of dyestufimixture 1.0 g. Dupanol .C (sodium lauryl sulfate) q. s. water to make 85m1. pH=6.25

In this mixture there was immersed for 20 minutes. at

80 F. a strip of white all wool fabric, which was thereafter rinsed tonearly colorless with water. Wool is not dyed by brief contact atordinary temperatures with the nearly neutral dyestui'f mixture To thenearly neutral dye-mixture were next added and Well-mixed 2.5 .mLof

concentrated ammoniaaqua to malre 87-88 ml. 11.3. A duplicate strip ofWhite, all-wool fabric wa's immersed.

therein for 20 minutes at 76 F. The wooLwas thereafter briefly dippedin5 percent acetic acid solution, and finally rinsed with warm tap water.The wool retained a faint grayish color. The wool is incipiently, butweak- 1y, dyed, at ordinary temperatures with'the weakly alkalinemixture of dyestufis.

To the ammoniacal dye mixture was next added, and

well mixed, 5 ml. of ammoniacal sodium thioglycolate: 30

solution carryingi 1.4 g. thioglycolic acid. 0.6 g, sodium hydroxide 0.4m1. concentrated ammonia aqua, to make 93 ml.

A triplicate strip-of white, all wool fabric was immersed for 20 minutesat 76 F. The wool was thereafter briefly dipped in 5% acetic acidsolution, then shampooed warm, and warm rinsed. The wool retained anintense, dull black color. Wool is deeply dyed at ordinary temperaturesby brief contact with the combination ofalkaline mercapto compound withthe dyestuffs.

Example XXI A solution was prepared carrying 0.300 g. D& Black #1 (c.1.246 0.088 g. D'& 0 Brown #1 c. I. 234 0.113 g. Ext. 13a 0 Red #13 o.I. 252

Total 0.501 g. of dyestuff mixture 1 1.0 g. Dupanol C (sodium laurylsulfate) 2.64 ml. concentrated ammonia aqua 0.1 g. thioglycolic acid0.03 g. sodium hydroxide q. s. water to make 100ml.

In the fresh mixture a strip of whit e, all wo ol fabric was immersedfor 20v minutes at .66? FL, thereafter dipped.

for minutes in 5% aqueous acetic acid at 66 F., finally shampooed inwarm water, rinsed, and dried. The wool thioglycolate used in ExampleExample XXII Wool was treated with the solution and by the methoddescribed in Example XXI at 50 F. for 15 minutes. After subsequentrinsing and drying, the wool retained a pronounced permanent, mediumgray coloration without any evident alteration of the texture orstrength.

Example XXIII Wool was treated with the solution and in the mannerdescribed in Example XXI at pH 8, and at a temperature of 110 F.', for15 'minutes. After rinsing and drying,

the wool retained abeautiful velvet black. It had been permanently dyed.No wool damage was evident. The dyed fabric remained soft and pliable.

Example XXIV' Wool was dyed in the solution and by the process describedinExample XXI at pH 6.6, and at a temperature of 110 F., for 15-minutes. Afterrinsing and drying, the wool retained a permanent, verydark reddish brown coloration, noticeably lighter than the velvet blackretained after the identical procedure with a corresponding solution atpH 8.0 as described in Example XXIII.

What is claimedis:

.1. A method forthe permanent dyeing of keratinousmaterial, whichcomprises treating the material to be dyed with a freshly preparedaqueous solution containing a quantity of a water soluble mercaptocompound oflow" toxicity equivalent .with. respect to, SH group toaboutture-between about 50 F. and 110 F;

3.; Method as claimed=in claiml, in. which the pH value of the solution.is maintained ,betweenB. and. 10.2.

4. A method, for the permanent dyeingof human hair.

which comprises, the. steps of treating the hairto be dyed,

at -.a temperature of between. about F. and 110 F,

with afreshly prepared aqueoussolutionofa quantity of awater-solublemercapto compound .of the group consisting of thioglycolicacid, thiosalicylicacid in the form of its water soluble salts,thioglycol, thioglycerol and thiophenolequivalenuwith;respecttoSI-Lgroup to about 1.2% to 6% retained adistinct, even, gray color, appreciably stronger. than the faint grayishcolor obtained intheentire absence. of thioglycolate, and much weaker,than the du ll black color obtained in the presence of the 1415 timesstronger by weight of the solution ofthioglycolic acid and containing,as sole coloringagent, about 0.033%, to about 6,2 by weight of thesolution of a dyestulfof the group consisting f theExt. n&' c, D & .Cand FD & c certified colors larld mixtures thereof, the solution havinga pI-I valu'e between 6.6 and 10.4 butnot higher than 9.4 when themercapto'concentration is equivalent to at least 3 by weight .of thesolution of thioglycolic acid and not higher than'f9,15 whenthe mercaptoconcentration is equivalent tofat least 5.6% byjweight of the solutionof thioglycolic acid,'then washingthe dyed hair with an aqueous mediumand drying the same.

5. A method. as claimed inclaim 4, in which the pH- value ofthesolutionis maintainedbetween. 9 and 10.2.;

6. A method as claimed in claim 4, in which the mercapto compound usedis thioglycolic acid.

7. A method for the permanent dyeing. of human hair which comprises thesteps of treating the hair to be dyed with afreshly'pjrepared aqueoussolution of a quantityof a water-soluble mercapto compound of the groupconsisting of thioglycolic acid, thiosalicylic acid in the form, of itswater-solublesalts, thioglycol, thioglycerol and thiophenol equivalentwithrespect to SH group to about 1.2%

to 6% by weight ofthe solution of thioglycolic acid and, containing, assole coloring agent, about 0.033% to about 6.2% by weightof the solutionof, a dyestuif of the group consisting of the Ext. D & C, D & C and F D&-C certified colors and mixtures thereof, said solution having a pHvalue between 6.6 and 10.4 but not higher than 9.4 when the mercaptoconcentration is equivalent to at least 3% by weight of the solution ofthioglycolic acid and not higher than 9.15 when the mercaptoconcentration is equivalent to at least 5.6% by weight of the solutionof thioglycolic acid, said solution being applied to the hair at atempera- 15 ture of between about 50 F. and 110 F. but not less than 70F. when both mercapto concentration and pH value approach their minimumvalues and not higher than 80 F. when both mercapto concentration and pHvalue approach their maximum values.

8. A method as claimed in claim 7, in which the pH value of the solutionis maintained between 9 and 10.2.

9. A method as claimed in claim 7, in which the dye solution is left incontact with the hair for a period of about minutes to about 35 minutes,

10. A method for the permanent dyeing of human hair which consists ofthe steps of treating the hair to be dyed at a temperature of betweenabout 50 F. and 110 F. with a freshly prepared aqueous solution of aquantity of a water-soluble mercapto compound of the group consisting ofthioglycolic acid, thiosalicylic acid in the form of its water-solublesalts, thioglycol, thioglycerol and thiophenol equivalent with respectto SH group to about 1.2% to 4% by Weight of the solution ofthioglycolic acid and containing, as sole coloring agent, about 0.033%to about 6.2% by weight of the solution of a dyestutf of the groupconsisting of the Ext. D & C, D & C and F D & C certified colors andmixtures thereof, said solution having a pH value of between 6.6 and10.4 but not higher than 9.4 when the mercapto concentration isequivalent to at least 3% by weight of the solution of thioglycolicacid, then Washing the dyed hair with an aqueous medium and drying thesame.

11. A method for the permanent dyeing of human hair which consists ofthe steps of treating the hair to be dyed at a temperature between about50 F. and 110 F. with a freshly prepared aqueous solution of a quantityof a Water-soluble mercapto compound of the group consisting ofthioglycolic acid, thiosalicylic acid in the form of its water-solublesalts, thioglycol, thioglycerol and thiophenol equivalent with respectto SH group to about 4% to 6% by weight of the solution of thioglycolicacid and containing, as sole coloring agent, about 0.033% to about 6.2%by weight of the solution of a dyestuff of the group consisting of theExt, D & C, D & C and F D & C certified colors and mixtures thereof,said solution having a pH value between 6.6 and 9.4 but not higher than9.15 when the mercapto concentration is equivalent to at least 5.6% byweight of the solution of thioglycolic acid, then treating the dyed hairwith a mild oxidizing agent, washing the hair with an aqueous medium anddrying the hair.

12. A preparation for the permanent dyeing of keratinous material in theform of an aqueous solution having a pH between about 6.6 and about 11.3and containing a quantity of a water-soluble mercapto compound of lowtoxicity equivalent with respect to SH group to about 0.1 to about 6% byweight of the solution of thioglycolic acid and, as sole coloring agent,about 0.033 to about 6.2% by weight of the solution of a dyestuff of thegroup consisting of the Ext. D & C, D & C and F D & C certified colorsand mixtures thereof.

13. A preparation for the permanent dyeing of human hair in the form ofa freshly prepared aqueous solution containing an amount of awater-soluble mercapto compound selected from the group consisting ofthioglycolic acid, thiosalicylic acid in the form of its water-solublesalts, thioglycol, thioglycerol and thiophenol equivalent with respectto SH group to about 1.2% to 6% by Weight of the solution ofthioglycolic acid and, as sole coloring agent, about 0;033% to about6.2% by weight of the solution of a dyestuff of the group consisting ofthe Ext. D & C, D & C and F D & C certified colors and mixtures thereof,said solution having a pH value between 6.6 and 10.4 but not higher than9.4 when the mercapto concentration is equivalent to at least 3% byWeight of the solution of thioglycolic acid and not higher than 9.15when the mercapto concentration is equivalent to at least 5.6% by weightof the solution of thioglycolic acid.

14. A preparation as claimed in claim 13, in which the solution has a pHvalue of between about 9 and 10.2.

15. A preparation for the permanent dyeing of keratinous material in theform of a substantially dry powdered mixture comprising a drywater-soluble solid mercapto compound of low toxicity, an ammonium salt,a dry, weakly alkaline water-soluble salt of an alkali metal, and, assole coloring agent, a dry dyestuff selected from the group consistingof the Ext. D & C, D & C and F D & C certified colors and mixturesthereof, the several ingredients being present in such proportions that,on addition of the dry powdered mixture to a predetermined quantity ofwater, a dye solution is formed which contains about 0.033% to about6.2% by weight of the solution of dyestutf and a quantity of mercaptocompound equivalent with respect to SH group to about 0.1% to about 6%by weight of the solution of thioglycolic acid and which has a pH valueof between about 6.6 and 11.3.

16. A preparation for the permanent dyeing of human hair in the form ofa substantially dry powdered mixture comprising a dry water-soluble saltof thioglycolic acid, an ammonium salt, a dry, weakly alkalinewatersoluble salt of an alkali metal, and, as sole coloring agent, a drydyestuff selected from the group consisting of the Ext. D & C, D & C andF D & C certified colors and mixtures thereof, the several ingredientsbeing present in such proportions that, on addition of the dry powderedmixture to a predetermined quantity of water, a dye solution is formedcontaining about 0.033 to 6.2% b. w. of dyestufi and about 1.2% to 6% byweight of the solution of thioglycolic acid and which has a pH value ofbetween about 6.6 and 10.4 but not higher than 9.4 when the thioglycolicacid concentration is at least 3% by weight of the solution and nothigher than 9.15 when the thioglycolic acid concentration is at least5.6% by weight of the solution.

17. A method for the permanent dyeing of keratinous material, whichcomprises the steps of preparing separately an aqueous dye solutioncontaining, as sole coloring agent, a dyestufi selected from the groupconsisting of the Ext. D & C, D & C and F D & C certified colors andmixtures thereof and a water solution of a Watersoluble mercaptocompound, the respective pH values of the two solutions, the totalquantity of solvent in both solutions, the relative proportions of thesolutions, the concentration of mercapto compound in the mercaptosolution and the concentration of dyestufi in the dye solution beingsuch that a mixture of the two solutions contains about 0.033% to about6.2% by weight of the solution of dyestuff and a quantity of mercaptocompound equivalent with respect to SH group to about 0.1% to about 6%by weight of the solution of thioglycolic acid and has a pH valuebetween about 6.6 and about 11.3, combining the two separate solutionsto form such mixture, applying the freshly prepared mixture to thekeratinous material to be dyed, washing the dyed material with anaqueous medium and drying the same.

18. A method for the permanent dyeing of human hair, which comprises thesteps of preparing separately an aqueous dye solution containing, assole coloring agent, a dyestutf selected from the group consisting ofthe Ext. D & C, D & C and F D & C certified colors and mixtures thereofand a Water solution of a water-soluble mercapto compound of the groupconsisting of thioglycolic acid, thiosalicylic acid in the form of itswatersoluble salts, thioglycol, thioglycerol and thiophenol, therespective pH values of the two solutions, the total quantity of solventin both solutions, the relative proportions of the solutions, theconcentration of mercapto compound in the mercapto solution and theconcentration of dyestuff in the dye solution being such that a mixtureof the two solutions contains about 0.033% to about 6.2% by weight ofthe solution of dyestutr and a quantity of mercapto compound equivalentwith respect to SH group to about 1.2% to about 6% by weight of themixed solution of thioglycolic acid and has a pH value of between about6.6 to 10.4 but not higher than 9.4 when the mercapto concentration inthe mixture is equivalent to at least 3% by Weight of the mixed solutionof thioglycolic acid and not higher than 9.15 when the mercaptoconcentration of the mixture is equivalent to at least 5.6% by weight ofthe mixed solution of thioglycolic acid, combining the two separatesolutions to form such a mixture, applying the fresh mixture to the hairto be dyed at a temperature about 50 and 110 F., washing the dyed hairwith an aqueous medium and drying the same.

References Cited in the file of this patent UNITED STATES PATENTS1,917,101 Niederhausern July 4, 1933 2,201,929 Speakrnan May 21, 19402,405,166 Reed Aug. 6, 1946 2,418,664 Ramsey Apr. 8, 1947 2,464,281Peterson Mar. 15, 1949 2,501,184 Michaels Mar. 21, 1950 2,577,710McDonough Dec. 4, 1951 2,610,941 Schueller Sept. 16, 1952 18 2,643,211Den Beste June 23, 1953 2,653,121 Schnell Sept. 22, 1953 FOREIGN PATENTS171,725 Austria June 25, 1952 117,071 Australia June 3, 1943 OTHERREFERENCES Windus et al.: The Unhairing Problem, Journal AmericanLeather Chem. Association, volume 33, 1938, pages 246 to 253.

Hall: The Monthly Review of Current Textile Progress, Textile Colorist,February 1942, pp. 63 to 65.

Hollenberg: Cold wave formulation, Drug and Cosmetic Industry, June1950, pgs. 664, 665 765-767, and 769, pg. 766; The coloring of the wavesolution presents a parallel problem with the great variety of certifiedapproved colors at our disposal, there are only a few that stand up inthese solutions 167-871 Speakman: Constitution, properties and uses ofwool, The Textile Manufacturer, April 1940, page 160.

Evans: Drug and Cosmetic Industry, June 1950, page 648.

Herriott: Advances in Protein Chemistry, vol. III, 1947, pages 182 and183.

1. THE METHOD FOR THE PERMANENT DYEING OF KERATINOUS MATERIAL, WHICHCOMPRISES TREATING THE MATERIAL TO BE DYED WITH A FRESHLY PREPAREDAQUEOUS SOLUTION CONTAINING A QUANTITY OF A WATER SOLUBLE MERCAPTOCOMPOUND OF LOW TOXICITY EQUIVALENT WITH RESPECT TO SH GROUP TO ABOUT0.1 TO ABOUT 6% BY WEIGHT OF THE SOLUTION OF THIOGLYCOLIC ACID AND, ASSOLE COLORING AGENT, ABOUT 0.033 TO ABOUT 6.2% BY WEIGHT OF THE SOLUTIONOF A DYESTUFF OF THE GROUP CONSISTING OF THE EXT. D & C, D & C, AND F D& C CERTIFIED, COLORS AND MIXTURES THEREOF, THE SOLUTION HAVING A PHVALUE BETWEEN ABOUT 6.6 AND ABOUT 11.3, THEN WASHING THE DYED MATERIALWITH AN AQUEOUS MEDIUM AND DRYING THE SAME.